CO2 electrochemical reduction by Zn-based layered double hydroxides: The role of structural trivalent metal ions

Carbon dioxide electrochemical reduction (CO 2 ER) has attracted considerable attention as a technology to recycle CO 2 into raw materials for chemicals using renewable energies. Zn-based layered double hydroxide (LDH) was recently found to be a promising CO 2 ER catalyst, which is a non-precious metal catalyst with excellent selectivity for carbon monoxide (CO). However, the role of structural trivalent metal ions (M 3+ ) contained in Zn-M 3+ LDHs for the CO 2 ER performance was not revealed. In this study, Zn-Cr, Zn-Ga LDHs, and Zn-Al LDHs were synthesized using a facile coprecipitation process, and their CO 2 ER performance and electrochemical properties were evaluated. We found that not only Zn-Al LDH but also Zn-Cr and Zn-Ga LDHs showed CO 2 ER activity for CO evolution, and the analysis by electrochemical impedance spectroscopy revealed that the type of M 3+ in Zn-based LDHs affected their electronic and ionic conductivity, functioning as key roles for their CO 2 ER performance.